1. Field
The present invention relates to an accelerator pedal apparatus applied to vehicles and the like having a drive-by-wire system, and in particular, relates to an accelerator pedal apparatus including a mechanism to generate reaction force (i.e., resistance force) opposed to tread force of an accelerator pedal in order to suppress excessive depression for improving fuel consumption and the like.
2. Description of the Related Art
For an engine mounted on an automobile and the like, an accelerator pedal apparatus applied to an electronically controlled throttle system (i.e., a drive-by-wire system) includes a pedal arm swingably supported to a housing, a return spring to return the pedal arm to a rest position, a hysteresis generating mechanism to generate hysteresis on pedal load (i.e., tread force), a position sensor to detect an angular position of the pedal arm and the like, so that a depression amount (i.e., an angular position) of a accelerator pedal (i.e., the pedal arm) is detected by the position sensor and engine output control is performed based on the detection signal as disclosed in Japanese Patent Publication No. 2004-155375.
Another accelerator pedal apparatus includes a reaction force adding mechanism as accelerator restriction means to restrict depression of an acceleration pedal by generating resistance force on tread force of the accelerator pedal as disclosed in Japanese Patent Publication No. 2007-137152. The reaction force adding mechanism includes a pedal arm swingably supported to a housing (i.e., a casing bracket), a support shaft swingably supporting the pedal arm, a coil-shaped return spring to return the pedal arm toward a rest position, a rod arranged to pass through the return spring and being capable of contacting to an upper end part of the pedal arm, a slider holding a rod and a second spring which urges the rod toward the pedal arm side, a lead screw rotatably supported to the housing for driving the slider to reciprocate and provided integrally with a gear, a motor fixed to the housing for rotationally driving a worm gear mated with the gear of the lead screw, and the like.
Here, the reaction force adding mechanism adopts a transmission path of driving force (i.e., pressing back force) from the worm gear to the slider and rod via the gear and lead screw. Therefore, the configuration becomes complicated and the apparatus becomes large. In addition, the responsibility is insufficient to be accepted.
When the reaction force adding mechanism disclosed in Japanese Patent Publication No. 2004-155375 is to be applied to the accelerator pedal apparatus disclosed in Japanese Patent Publication No. 2007-137152, the configuration becomes further complicated to be adopted and is difficult to be applied as-is, since the accelerator pedal apparatus is provided with the hysteresis generating mechanism. In addition, in the case that both of the hysteresis generating mechanism and the reaction force adding mechanism are provided, it is necessary to ensure independency of respective functions so as not to affect to one mechanism from the other.
Accordingly, it has been desired to develop an accelerator pedal apparatus of quick response with a simple and downsized configuration while a hysteresis generating mechanism and a reaction force adding mechanism reliably function respectively. In particular, the accelerator pedal apparatus is desired to include a reaction force adding mechanism to add reaction force opposed to tread force in order to suppress excessive depression for improving fuel consumption and the like.